1. Field of the Invention
The present invention relates to a soluble polythiophene derivative having coplanar groups, and in particular relates to a photoelectric device utilizing the same.
2. Description of the Related Art
Because polymeric semiconductor materials have semiconductor and photoelectric properties, they can be applied in many photoelectric devices such as organic thin-film transistors (abbreviated OTFT), organic solar cells, organic light emitting diodes (abbreviated OLED), and photo sensors. Due to its polymer properties, polymeric semiconductor materials are utilized to form active film coated on photoelectric devices, Photoelectric devices utilizing polymeric semiconductor materials have advantages such as having a light weight, being inexpensive, being easy to fabricate, and flexibility along with suitability for large area fabrication. Conjugated polymer having a conjugated backbone is one of the most popularly used polymeric semiconductor material in photoelectric devices. However, conjugated polymer has disadvantages such as low carrier mobility, and a narrow absorption band of about 400 nm to 650 nm. Therefore, many conjugated polymers are synthesized to enhance carrier mobility and absorption band thereof, to further improve photoelectric efficiency when applied.
For solar cell applications, characteristics such as high electron/hole mobility and wide absorption band are desired for improving the power conversion efficiency thereof. Thus, an electron donor material such as polymer is often combined with an electron acceptor material such as C60 by heterojunction technology. For example, the electron donor material poly(3-hexylthiophene) (abbreviated P3HT) blended with [6,6]-phenyl-C61-butyric acid methyl ester (abbreviated PCBM) has a power conversion efficiency of 3.5%.
P3HT, poly(9,9-dioctylfluorenyl-dithiophene) (abbreviated F8T2), and poly(cyclopentyldithiophene derivative) (abbreviated PCPDTBT) are formed from polymerizing thiophene derivatives, such that the polymers have a cyclo conjugated thiophene backbone. The polymer long chains thereof are attracted to each other, thereby enhancing intermolecular π-π interaction and carrier mobility of the polymer. In 2006, YongFanf Li disclosed a coplanar polythiophene having conjugated side chains in Synthesis and photovoltaic properties of two-dimensional conjugated polythiophenes with bi(thienylenevinylene) side chains, J. H. Hou, Z. A. Tan, Y. Yan, Y. J. He, C. H. Yang, Y. F. Li, J. Am. Chem. Soc. 128 (2006) 4911. Li also disclosed that the conjugated side groups may widen the absorption band, resulting in improved power conversion efficiency of the polymer.